The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure. Unless otherwise indicated herein, the approaches described in this section are not prior art to the claims in the present disclosure and are not admitted to be prior art by inclusion in this section.
In device-to-device (D2D) communication, the following two-step transmission of direct data may be used. First, a scheduling assignment (SA) or a physical sidelink control channel (PSCCH) transmission that includes control information may be transmitted from a transmitting user equipment (UE) to a receiving UE. The SA or PSCCH transmission may include control information that the receiving UE may need to receive a data transmission from the transmitting UE. Next, the transmitting UE may transmit data according to the SA or PSCCH control information. In some cases, the UE transmissions of the SA, PSCCH, and/or data may be based on resources allocated by an evolved NodeB (eNB), which is referred to herein as Mode-1 operation. In other cases, the transmissions of the SA, PSCCH, and/or data may be based on resources allocated by the UE, which is referred to herein as Mode-2 operation.
As used herein, D2D communication may also be referred to as “sidelink” communication. Such communication shall be referred to herein as D2D communication for the sake of consistency.